"Pre-computation attacks are a somewhat new and interesting phenomenon
we are starting to encounter 'in the wild' through chainsaw security
consultants. What they do is they pre-compute all of the possible LM
NT password hashes of a given length with a given character set and
the pre-computed password-hash-to-password-mappings to DVD. Heck they
can even submit their request to have your password hash reversed back
into a password using a web page someone has setup to do the job for
(sorry, not going to give out THAT URL here.) . . . for free!"